el7155 Intersil Corporation, el7155 Datasheet - Page 8

• Manufacturer Part Number: el7155
• Description: High Performance Pin Driver
• Manufacturer: Intersil Corporation

Applications Information
Product Description
The EL7155 is a high performance 40MHz pin driver. It
contains two analog switches connecting V
V
two switches will be closed and the other switch open. An
output enable (OE) is also supplied which opens both
switches simultaneously.
Due to the topology of the EL7155, V
connected to a voltage equal to, or lower than GND. V
be connected to any voltage between V
supply, V
The EL7155 is available in both the 8 Ld SO and the 8 Ld
PDIP packages. The relevant package should be chosen
depending on the calculated power dissipation.
3-state Operation
When the OE pin is low, the output is 3-state (floating.) The
output voltage is the parasitic capacitance’s voltage. It can
be any voltage between V
previous state. At 3-state, the output voltage can be pushed
to any voltage between V
be pushed higher than V
diode at the output stage will turn on.
Supply Voltage Range and Input Compatibility
The EL7155 is designed for operation on supplies from 5V to
15V (4.5V to 16.5V maximum). The table on page 6 shows
the specifications for the relationship between the V
V
All input pins are compatible with both 3V and 5V CMOS
signals. With a positive supply (V
also compatible with TTL inputs.
Power Supply Bypassing
When using the EL7155, it is very important to use adequate
power supply bypassing. The high switching currents
developed by the EL7155 necessitate the use of a bypass
capacitor between the V
recommended that a 2.2µF tantalum capacitor be used in
parallel with a 0.1µF low-inductance ceramic MLC capacitor.
These should be placed as close to the supply pins as
possible. It is also recommended that the V
have some level of bypassing, especially if the EL7155 is
driving highly capacitive loads.
L
L
, and GND pins.
to OUT
S
L
+.
. Depending on the value of the IN pin, one of the
S
H
H
+ and GND pins. It is
H
or lower than V
and V
and V
8
S
L
L
. The output voltage can’t
+) of 5V, the EL7155 is
, depending on the
L
should always be
L
and the positive
L
H
H
since the body
to OUT
and V
L
S
H
+, V
pins
H
and
can
H
,
EL7155
Power Dissipation Calculation
When switching at high speeds, or driving heavy loads, the
EL7155 drive capability is limited by the rise in die
temperature brought about by internal power dissipation. For
reliable operation die temperature must be kept below
T
dissipation for a given application prior to selecting the
package type.
Power dissipation may be calculated:
where:
Having obtained the application’s power dissipation, a
maximum package thermal coefficient may be determined,
to maintain the internal die temperature below T
where:
θ
PDIP8 package when using a standard JEDEC JESD51-3
single-layer test board. If T
calculated using the equation above, then one of the
following actions must be taken:
PD
θ
JA
JMAX
JA
V
GND)
V
C
C
I
f is frequency
T
T
PD is the power dissipation calculated above
θ
Reduce θ
into the PCB (as compared to the standard JEDEC
JESD51-3)
Use the PDIP8 instead of the SO8 package
De-rate the application either by reducing the switching
frequency, the capacitive load, or the maximum operating
(ambient) temperature (T
S
JA
S
OUT
JMAX
MAX
L
INT
=
is 160°C/W for the SO8 package and 100°C/W for the
=
is the quiescent supply current (3mA max)
is the load capacitance
is the total power supply to the EL7155 (from V
(
thermal resistance on junction to ambient
(
----------------------------------------------
V
(125°C). It is necessary to calculate the power
T
is the internal load capacitance (100pF max)
S
is the swing on the output (V
is the maximum operating temperature
JMAX
is the maximum junction temperature (125°C)
×
I
JA
S
PD
)
–
the system by designing more heat-sinking
+
T
(
MAX
C
INT
)
×
V
S
JMAX
2
MAX
×
f )
)
+
is greater than 125°C when
(
C
L
H
×
- V
V
OUT
L
)
2
×
JMAX
f )
March 9, 2006
S
:
FN7279.2
+ to